Sheet feeder and image forming apparatus including the same

ABSTRACT

In a sheet feeder that feeds a sheet to an image forming apparatus, a sheet placing table has a placement surface on which a sheet is placed and is inclined downward toward a downstream side in a sheet feeding direction. A sheet detecting unit has an operation piece that presses a leading end of the sheet toward an upstream side in the sheet feeding direction with predetermined pressure. A regulating member is arranged in a vicinity of an end part of the sheet placing table on the upstream side in the sheet feeding direction. The regulating member regulates movement of the sheet to the upstream side in the sheet feeding direction and has regulating portions having different heights from the placement surface of the sheet placing table. The regulating portions are arranged so that the heights are increased toward the upstream side in the sheet feeding direction.

BACKGROUND 1. Field

The present disclosure relates to a sheet feeder that feeds a sheet to an image forming apparatus and an image forming apparatus including the same, and particularly relates to a structure by which presence or absence of a sheet that is placed on a sheet placing table is accurately detected.

2. Description of the Related Art

As a sheet feeder of the related art, in Japanese Unexamined Patent Application Publication No. 8-53232, a sheet feeding cassette is included and a rear end regulating plate is arranged at a rear end position of the sheet feeding cassette so as to be movable in a forward and backward direction. In this configuration, after a sheet bundle is loaded on the sheet feeding cassette, the rear end regulating plate is moved forward to be pressed against and brought into contact with a rear end of the sheet bundle, and thus a leading end part of the sheet bundle is reliably positioned at a tip end part of the sheet feeding cassette.

Additionally, in Japanese Unexamined Patent Application Publication No. 2010-70281, in the middle of a sheet feeding path for taking a sheet from a manual tray to an image forming apparatus, a friction member is arranged on an upper surface of a bottom plate constituting the sheet feeding path. In this configuration, feeding of the lower last sheet together with the upper sheet when there are the last two sheets on the bottom plate is suppressed by a frictional force of the friction member on the upper surface of the bottom plate.

Some sheet feeders have a configuration that includes a mechanism that detects presence or absence of a sheet on a sheet placing table such as a sheet feeding cassette or a manual tray. In this mechanism, the sheet placing table is arranged so as to be inclined downward toward a downstream side in a sheet feeding direction and an operation piece by which a leading end part of a sheet that is placed on the sheet placing table is pressed toward an upstream side in the sheet feeding direction with predetermined pressure is provided. In the configuration, whereas when there is no sheet, the operation piece is at an initial position, to which the operation piece has been moved to the upstream side in the sheet feeding direction with the predetermined pressure, when a large number of sheets are placed, the operation piece is pushed back (to a downstream side in a conveyance direction) from the initial position by weights of the sheets against the predetermined pressure, and thus placement of a sheet is detected.

However, in a case where the number of sheets that are placed is small, for example, one or two, weights of the sheets are light, and therefore the operation piece is moved to the initial position with the predetermined pressure in some cases. Accordingly, in this case, erroneous detection that there is no sheet on the sheet placing table is performed.

Then, by utilizing a technique of Japanese Unexamined Patent Application Publication No. 8-53232, it is considered that a rear end regulating plate is arranged at a rear end of the sheet placing table. However, in this consideration, adjustment such that a position of the rear end regulating plate is manually moved in a forward and backward direction is desired each time a sheet having a different length in the sheet feeding direction is placed on the sheet placing table, which is troublesome. Particularly, in a case where the sheet placing table is a manual tray, since a sheet having a different size is frequently placed, it is troublesome to move the rear end regulating plate each time the placement is performed.

In addition, by utilizing a technique of Japanese Unexamined Patent Application. Publication. No. 2010-70281, it is also considered that a friction member (friction sheet) is arranged on a placement surface of the sheet placing table. However, since the friction member generates a frictional force with a lower surface of a last sheet, for example, in a case where some separation is generated between the last sheet and the friction member and the last sheet floats, the operation piece is easily moved toward the upstream side in the sheet feeding direction with the predetermined pressure, and therefore there is a concern that detection of a sheet is not reliable.

In view of the aforementioned points, the disclosure provides a configuration of a sheet feeder, by which even in a case where sizes (lengths in a sheet feeding direction) of sheets are various or even in a case where the number of sheets is small, only by placing a sheet on a sheet placing table, presence of the sheet is able to be reliably detected without performing any manual operation.

SUMMARY

A sheet feeder according to an aspect of the disclosure is a sheet feeder that feeds a sheet to an image forming apparatus and includes: a sheet placing table that has a placement surface on which a sheet is placed and that is inclined downward toward a downstream side in a sheet feeding direction in which the sheet is fed to the image forming apparatus; a sheet detecting unit that has an operation piece which presses an end of the sheet on the downstream side in the sheet feeding direction toward an upstream side in the sheet feeding direction with predetermined pressure and that detects presence or absence of the sheet an operation of the operation piece; and a regulating member that is arranged in a vicinity of an end part of the sheet placing table on the upstream side in the sheet feeding direction and that regulates movement of the sheet to the upstream side in the sheet feeding direction, in which the regulating member has a plurality of regulating portions having different heights from the placement surface of the sheet placing table, and the plurality of regulating portions are arranged so that the heights are increased toward the upstream side in the sheet feeding direction.

In the aforementioned configuration, the sheet placing table is inclined downward toward the downstream side in the sheet feeding direction. Then, in a case where a sheet is placed on the sheet placing table, an end of the sheet on the upstream side in the sheet feeding direction is placed to be positioned within an arrangement range of the plurality of regulating portions of the sheet placing table.

Then, in this state, in a case where a large number of sheets are placed on the sheet placing table, that is, in a case where pressure to the downstream side in the sheet feeding direction, which is caused by weights of the sheets, exceeds the predetermined pressure, the operation piece is moved to the downstream side in the sheet feeding direction by the weights of the sheets, and therefore the sheet detecting unit accurately detects presence of the sheets.

On the other hand, in a case where the number of sheets on the sheet placing table is small, for example, one or two, that is, in a case where the pressure to the downstream side in the sheet feeding direction, which is caused by the weights of the sheets, is lower than the predetermined pressure, the operation piece pushes back a leading end part (end part on the downstream side in the sheet feeding direction) of the sheet to the upstream side in the sheet feeding direction, but when a rear end part (the end part on the upstream side in the sheet feeding direction) of the sheet is locked by any of the regulating portions of the regulating member arranged on the sheet placing table, movement of the sheet is regulated or stopped by the regulating portion. Accordingly, since the operation piece is not moved further to the upstream side in the sheet feeding direction, the sheet detecting unit accurately detects presence of the sheets on the sheet placing table.

Here, the regulating member is composed of the plurality of regulating portions, and the regulating portions are arranged so that the heights (heights from the placement surface of the sheet placing table) are increased toward the upstream side in the sheet feeding direction. Accordingly, in a case where sheets to be placed on the sheet placing table have variously different lengths in the sheet feeding direction, for example, in a case where the sheets have a standard size, such as a postcard, but have tolerance (for example, about 1.5 mm), and in a case where some positional displacement in the sheet feeding direction occurs between a plurality of sheets to be placed, and moreover, even in a. case where sheets that have different lengths in the sheet feeding direction and are variously customized are selectively placed, end parts of such sheets on the upstream side in the sheet feeding direction are reliably locked by any of the plurality of regulating portions. Therefore, even in a case where various sheets that have different lengths in the sheet feeding direction are selectively placed on the sheet placing table, it is not desired to move or adjust, as the related art, the regulating member in a forward and backward direction each time the placement is performed. Moreover, since any of the plurality of regulating portions locks a rear end of a sheet, even in a case where the sheet floats slightly from the placement surface of the sheet placing table, it is possible to reliably regulate and stop movement of the sheet to the upstream side in the sheet feeding direction compared to a configuration of the related art in which a friction member is arranged on a placement surface.

In a case where there is no sheet on the sheet placing table, the operation piece is moved to the upstream side in the sheet feeding direction with predetermined pressure to be moved by all expected moving amount, and therefore the sheet detecting unit accurately detects absence of a sheet on the sheet placing table.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view illustrating an image forming apparatus that includes a sheet feeder of Embodiment 1;

FIG. 2 is a side view schematically illustrating a periphery of a manual feeder as the sheet feeder;

FIG. 3 is a plan view schematically illustrating the periphery of the manual feeder;

FIG. 4 is a sectional side view illustrating a specific configuration, in which the periphery of the manual feeder is enlarged;

FIG. 5 is a sectional side view illustrating a periphery of a sheet presence/absence detecting actuator, which is included in the manual feeder, in an enlarged manner;

FIG. 6 is a sectional side view in which a periphery of a regulating member that is included in the manual feeder is enlarged;

FIG. 7 is a sectional side view illustrating a periphery of a regulating member that is included in a manual feeder of Embodiment 2; and

FIG. 8 is a sectional side view illustrating a periphery of a regulating member that is included in a manual feeder of Embodiment 3.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, Embodiments of the disclosure will be described with reference to the drawings.

Embodiment 1

FIG. 1 is a sectional view illustrating an image forming apparatus that includes a sheet feeder according to Embodiment 1.

In the figure, an image forming apparatus 1 has a copy function by which a document is read and printed on a recording sheet and includes a document reading device 2, an automatic document feeder (ADF) 3, a printing unit 4, a sheet feeder 5, a manual feeder (sheet feeder) 7, a sheet conveyance unit 8, and the like. The document reading device 2 and the automatic document feeder 3 are mounted on an upper side of a body of the image forming apparatus 1. The printing unit 4, the sheet feeder 5, and the sheet conveyance unit 8 are incorporated in the body of the image forming apparatus 1. Furthermore, the manual feeder 7 is attached to a side wall of the body of the image forming apparatus 1.

Image data that is handled by the image forming apparatus 1 corresponds to a color image using respective colors of black (K), cyan (C), magenta (M), and yellow (Y), or corresponds to a monochromatic image using a single color (such as black). Thus, in the printing unit (image forming unit) 4, in order to form four kinds of toner images corresponding to the respective colors, four developers 12, four photosensitive drums 13, four drum cleaners 14, four chargers 15, and the like are provided to form four image stations Pa, Pb, Pc, and Pd respectively corresponding to black, cyan, magenta, and yellow.

In each of the image stations Pa, Pb, Pc, and Pd, after a drum cleaner 14 removes and collects residual toner on a surface of a photosensitive drum 13, a charger 15 uniformly charges the surface of the photosensitive drum 13 to predetermined potential, an optical scanner 11 exposes the surface of the photosensitive drum 13 to form an electrostatic latent image on the surface, and a developer 12 develops the electrostatic latent image on the surface of the photosensitive drum 13 to form a toner image on the surface of the photosensitive drum 13. Thus, toner images of the respective colors are formed on surfaces of the photosensitive drums 13.

Thereafter, a belt cleaner 22 removes and collects residual toner on an intermediate transfer belt 21 while the intermediate transfer belt 21 is moved to go around in a direction of an arrow C, and the toner images of the respective colors, which are formed on the surfaces of the photosensitive drums 13, are transferred onto the intermediate transfer belt 21 to form a color toner image on the intermediate transfer belt 21.

A nip area is formed between the intermediate transfer belt 21 and a transfer roller 23 a of a secondary transfer device 23, and the color toner image on a surface of the intermediate transfer belt 21 is transferred onto a recording sheet, which is conveyed through a sheet conveyance path R1 having an S-shape, while the recording sheet is pinched in the nip area and conveyed. Then, the recording sheet is pinched between a heat roller 24 and a pressure roller 25 of a fixing device 17 so as to be heated and pressurized, and therefore the color toner image on the recording sheet is fixed.

On the other hand, in the sheet conveyance unit (taking-in unit) 8, a recording sheet is fed from the sheet feeder 5 or the manual feeder 7, is conveyed through the sheet conveyance path R1 to be taken in, passes through the secondary transfer device 23 and the fixing device 17, and is discharged to a sheet discharge tray 39 by sheet discharge rollers 36. In the sheet conveyance path R1, resist rollers 34 which temporarily stop the recording sheet to align a leading end of the recording sheet and then start conveyance of the recording sheet so as to match a timing when the toner image is transferred in the nip area between the intermediate transfer belt 21 and the transfer roller 23 a, conveyance rollers 35 which prompt conveyance of the recording sheet, the sheet discharge rollers 36, and the like are arranged.

The sheet feeder 5 includes a cassette 51 that is arranged in a lower part of the image forming apparatus 1, a sheet feeding tray 52 on which a recording sheet is loaded, a pick-up roller 53 that is provided above one end of the sheet feeding tray 52, a sheet feeding roller 54 that is arranged on a downstream side of the pick-up roller 53 in a sheet conveyance direction (hereinafter, referred to as a sheet feeding direction), a separation roller 55 that is in pressure contact with the sheet feeding roller 54, and the like. In the sheet feeder 5, a recording sheet is drawn out from the sheet feeding tray 52 by the pick-up roller 53 to be guided to the sheet feeding roller 54. Each recording sheet is passed between the sheet feeding roller 54 and the separation roller 55 to be separated one by one, and is then fed to the sheet conveyance path R1.

Additionally, the manual feeder 7 is arranged on the side wall of the body of the image forming apparatus 1 and includes a manual tray (sheet placing table) 71 on which a recording sheet (sheet) is loaded, a sheet feeding roller 72 that is provided above one end of the manual tray 71, a separation roller 73 that is in pressure contact, with the sheet feeding roller 72, a sheet guiding member 74 that is arranged on an upstream side of a nip area between the sheet feeding roller 72 and the separation roller 73 in the sheet feeding direction of the recording sheet, and the like. In the manual feeder 7, by rotation of the sheet feeding roller 72 in a clockwise direction F in the figure, a recording sheet is guided from the manual tray 71 to the nip area between the sheet feeding roller 72 and the separation roller 73 via the sheet guiding member 74. Each recording sheet is passed through the nip area to be separated one by one, and is then fed to the sheet conveyance path R1.

Next, the manual feeder 7 which is Embodiment 1 of the sheet feeder of the disclosure will be described in detail. FIG. 2 is a side view schematically illustrating the manual feeder 7.

As illustrated in FIG. 2, the manual tray 71 is arranged so as to be inclined with a tip end part 71 a thereof disposed downward. In the tip end part 71 a, from an upstream side in a sheet feeding direction E of a recording sheet, a first inclined contact portion 71 b, a second inclined contact portion 71 c, and a third inclined contact portion 71 d are provided in order. On an upper surface of the manual tray 71, a pair of guide plates 75 that sandwich and guide the recording sheet are provided. The guide plates 75 are provided so as to be movable in a direction orthogonal to the sheet feeding direction E, are moved symmetrically with respect to a center of the manual tray 71 in an interlocked manner by a mechanism that is not Illustrated, and match a center of the recording sheet sandwiched between the guide plates 75 with the center of the manual tray 71.

The sheet feeding roller 72 is arranged above the third inclined contact portion 71 d of the tip end part 71 a of the manual tray 71, and the separation roller 73 is arranged below the sheet feeding roller 72. The separation roller 73 has a shaft 73 a that is parallel to a drive shaft 72 a of the sheet feeding roller 72, and a spring (not illustrated) urges a bearing (not illustrated) of the shaft 73 a of the separation roller 73 toward the sheet feeding roller 72, and therefore the separation roller 73 is brought into pressure contact with the sheet feeding roller 72, and thus a nip area H is formed between the sheet feeding roller 72 and the separation roller 73.

The third inclined contact portion 71 d has an upper end part fixed with the sheet guiding member 74, the sheet guiding member 74 extends toward a surface of the sheet feeding roller 72, and a tip end of the sheet guiding member 74 contacts the surface of the sheet feeding roller 72 or is slightly separated from the surface.

FIG. 3 is a plan view schematically illustrating a periphery of the manual feeder 7. FIG. 4 is a side view illustrating a specific configuration, in which the periphery of the manual feeder 7 is enlarged. As illustrated in FIG. 3, in the manual feeder 7, the manual tray 71 is formed in a rectangular shape that is long in the direction (hereinafter, also referred to as a lateral width. direction) orthogonal to the sheet feeding direction E. A length of the manual tray 71 in the sheet feeding direction E is set to about a length of a small-sized recording sheet, for example, such as an A6 size recording sheet. The upper surface of the manual tray 71 is formed to be an almost planer surface, and the planer surface is a placement surface 71 g on which a recording sheet is faced. As illustrated in FIG. 4, when a small-sized recording sheet Ps is placed on the placement surface 71 g, an end part (hereinafter, also referred to as a rear end part) of the recording sheet Ps on the upstream side in the sheet feeding direction E is positioned at a rear end part of the manual tray 71. Additionally, a configuration is provided such that the pair of guide plates 75 are provided on the placement surface 71 g and a center of a recording sheet is positioned on a center line 1 in the width direction on the placement surface 71 g by the guide plates 75.

Furthermore, on the upstream side of the manual tray 71 in the sheet feeding direction E, an extension tray (extended sheet placing table) 80 that is formed in a rectangular shape is arranged. The extension tray 80 has two connection portions 80 a and 80 b, each of which has a shape protruding in the sheet feeding direction E, at an end part (hereinafter, referred to as a front end part) on the downstream side in the sheet feeding direction E. The two connection portions 80 a and 80 b are formed at a left end part and a right end part (one end part and the other end part in the direction orthogonal to the sheet feeding direction E) of the extension tray 80 and are rotatably supported around shaft supporting points (not illustrated) that are formed at the rear end part of the manual tray 71. In the two connection portions 80 a and 80 b, bulging portions 80 c and 80 d each of which has a shape bulging upward are respectively formed as illustrated also in FIG. 4. An upper surface of the extension tray 80 is formed in a planer surface except for the bulging portions 80 c and 80 d, and the planer surface is a placement surface 80 e on which a rear part of a large-sized recording sheet is placed.

In FIG. 3, the sheet feeding roller 72 is arranged near a downstream end of the manual tray 71 in the sheet feeding direction E. Additionally, a center of the sheet feeding roller 72 is positioned on an extension line of the center line 1 of the manual tray 71.

FIG. 4 illustrates a state where the manual tray 71 and the extension tray 80 are opened. Though not illustrated in detail, the manual tray 71 has a lower end part rotatably supported by a side wall 1 a that forms a side wall of the body of the image forming apparatus 1 and is positioned at a closed position at which the manual tray 71 is accommodated in the side wall 1 a of the image forming apparatus 1 or an opened position which is illustrated and to which the manual tray 71 is rotated around a shaft supporting point in the clockwise direction in FIG. 4 from the closed position.

On the other hand, the extension tray 80 is positioned at an accommodation position at which the extension tray 80 is positioned directly above the manual tray 71 in an overlapping manner or an extension position. which is illustrated and to which the extension try 80 is rotated around the shaft supporting points in the clockwise direction in FIG. 4 to form a continuous placement surface by the manual tray 71 and the extension tray 80.

In a case where a recording sheet is fed by using the manual feeder 7, the manual tray 71 is positioned at the opened position that is illustrated and the extension tray 80 is further positioned at the extension position from the accommodation position. In this state, the small-sized recording sheet Ps is placed on the placement surface 71 g of the manual tray 71. On the other hand, in a case of a large-sized recording sheet Pl which is a sheet to be placed and a rear end part of which protrudes from the rear end part of the manual tray 71, a front part of the large-sized recording sheet Pl is placed on the placement surface 71 g of the manual tray 71 and a rear part thereof is placed on the placement surface 80 e of the extension tray 80. At this time, the rear part of the large-sized recording sheet Pl is placed on the placement surface 80 e in a state of being lifted upward in contact with the bulging portions 80 c and 80 d respectively formed on the two contact portions 80 a and 80 b of the extension tray 80.

As understood from FIG. 4, when being at the opened position that is illustrated, the manual tray 71 is positioned so that the rear end part thereof is positioned above the shaft supporting point (not illustrated) of a tip end part and an entirety of the manual tray 71 is inclined by an inclination angle θ1 toward the downstream side in the sheet feeding direction E. Accordingly, in a case where the small-sized recording sheet Ps is placed on the placement surface 71 g of the manual tray 71, the recoding sheet Ps moves toward the downstream side in the sheet feeding direction E by its own weight.

When being at the extension post ton that is illustrated, the extension tray 80 is also positioned so that a rear end part thereof is positioned above the shaft supporting points (not illustrated) of a tip end part and an entirety of the extension tray 80 is inclined by an inclination angle θ2 toward the downstream side in the sheet feeding direction E. The inclination angle θ2 of the extension tray 80 is set to an angle (θ2>θ1) which is different from the inclination angle θ1 of the manual tray 71 and larger than the inclination angle θ1 of the manual tray 71.

As illustrated in FIG. 4, in a vicinity of a front end part of the manual tray 71, a sheet detecting unit 90 is arranged so as to face the front end part. The sheet detecting unit 90 is arranged on a side of the sheet feeding roller 72 (in the direction orthogonal to the sheet feeding direction E) as illustrated in FIG. 3 and includes a sheet presence/absence detecting actuator (operation piece) 91.

As illustrated in detail in FIG. 5 in an enlarged manner, the sheet presence/absence detecting actuator 91 is composed of a chevron-shaped plate 91 a that is bent in a chevron shape, a connecting plate 91 b in a quadrilateral shape, and an urging spring 91 c. The chevron-shaped plate 91 a is composed of a horizontal plate 91 d that is arranged almost in parallel to the sheet feeding direction E and a rising plate 91 e that rises upward from an end part of the horizontal plate 91 d on the upstream side in the sheet feeding direction E, and a leading end part of the recording sheet Ps or Pl on the manual tray 71 contacts a vicinity of a lower end part of toe rising plate 91 e by its own weight or the like. The horizontal plate 91 d of the chevron-shaped plate 91 a has an end part on the downstream side in the sheet feeding direction E fixed to a shaft 92 that is provided in the body of the image forming apparatus 1 Additionally, the connecting plate 91 b also has a lower end part connected to the shaft 92 and has an upper end part in which a notch portion 91 f is formed so as to be opened toward the downstream side in the sheet feeding direction E. The urging spring 91 c is compressed and fitted between the notch portion 91 f and the body of the image forming apparatus 1.

In the sheet presence/absence detecting actuator 91, the connecting plate 91 b rotates toward the upstream side in the sheet feeding direction E by urging force (predetermined pressure) of the urging spring 91 c with the shaft 92 as a center, and the shaft 92 rotates in the clockwise direction accordingly, and therefore the chevron-shaped plate 91 a rotates toward the upstream side in the sheet feeding direction E to push back the leading end part of the recording sheet Ps or Pl on the manual tray 71 toward the upstream side in the sheet feeding direction E.

In a case where there is no recording sheet Ps nor Pl on the placement surface 71 g of the manual tray 71, the chevron-shaped plate 91 a of the sheet presence/absence detecting actuator 91 is positioned at the initial position, to which the chevron-shaped plate 91 a has completely rotated toward the upstream side in the sheet feeding direction E, by the urging force of the urging spring 91 c. On the other hand, in a case where there are a large number of small-sized recording sheets Ps or there is a large-sized recording sheet Pl on the placement surface 71 g of the manual tray 71, the chevron-shaped plate 91 a receives pressing toward the downstream side in the sheet feeding direction E, which is caused by a weight of the recording sheets Ps or the recording sheet Pl, and thus rotates toward the downstream side in the sheet feeding direction E while compressing the urging spring 91 c, and therefore the chevron-shaped plate 91 a is deviated from the initial position. The sheet detecting unit 90 includes a position sensor (not illustrated) that detects a position of the chevron-shaped plate 91 a of the sheet presence/absence detecting actuator 91, and the position sensor detects, when the chevron-shaped plate 91 a is at the initial position, absence of the recording sheet Ps or Pl on the placement surface 71 g of the manual tray 71 and detects, when the chevron-shaped plate 91 a is deviated from the initial position, presence of the recording sheet Ps or Pl.

In the sheet presence/absence detecting actuator 91, an operation amount of the chevron-shaped plate 91 a, that is, a moving amount from the initial position to a pressed position to which the chevron-shaped plate 91 a rotates until the urging spring 91 c is completely compressed by the pressing toward the downstream side in the sheet feeding direction E, which is caused by the weight of the recording sheet Ps or Pl, is set to about 1.5 mm, which is not more than 2 mm, for example.

As illustrated in FIG. 3, two regulating members 100 that regulate movement of the small-sized recording sheet Ps, which are placed on the placement surface 71 g, toward the upstream side in the sheet feeding direction E are arranged near the rear end part of the manual tray 71, that is, near the connection portions of the manual tray 71 and the extension tray 80. The regulating members 100 are positioned at a space sandwiched by the two connection portions 80 a and 80 b of the extension tray 80 in the direction orthogonal to the sheet feeding direction E. The two regulating members 100 are arranged one by one in a right-and-left direction (direction orthogonal to the sheet feeding direction E) across the center line 1 of the manual tray 71. Accordingly, the two regulating members 100 are symmetrically positioned across the sheet feeding roller 72 on the center line 1. Furthermore, the two regulating members 100 are arranged in such a manner that, in a case where a recording sheet Ps that has a minimum lateral width is positioned on the center line 1 by the pair of guide plates 75, the two regulating members 100 are positioned within the lateral width of the recording sheet Ps. Additionally, one regulating member 100 is positioned on a line extending from an arrangement position of the sheet presence/absence detecting actuator 91 toward the upstream side in the sheet feeding direction E.

Structures of the two regulating members 100 are mutually the same. FIG. 6 is a sectional side view in which a periphery of the regulating member 100 is enlarged.

In FIG. 6, the regulating member 100 is formed in a saw-tooth shape in which a large number of teeth are continuously aligned on a straight line in the sheet feeding direction E. Each of the large number of teeth constitutes a regulating portion 101 that regulates movement of a rear end part of each of various recording sheets Ps, which are different in a length in the sheet feeding direction E, toward the upstream side in the sheet feeding direction E. Each of the regulating portions 101 includes a steep surface 101 a that rises steeply in an almost vertical direction in a state where the manual tray 71 is inclined by the inclination angle θ1 and a rear inclined surface 101 b that obliquely descends downward and backward from a vertex of the steep surface 101 a. The steep surface 101 a has a function of regulating or stopping movement of a recording sheet Ps on the manual tray 71 toward the upstream side in the sheet feeding direction F by facing a rear end of the recording sheet Ps and contacting a rear end surface of the recording sheet Ps when the recording sheet Ps moves to the upstream side in the sheet feeding direction E.

The large number of regulating portions 101 are different from each other in a height h from the placement surface 71 g of the manual tray 71, that is, in a length from the placement surface 71 g to the vertex of the steep surface 101 a and the large number of regulating portions 101 are arranged so that heights h are increased toward the upstream. side in the sheet feeding direction E.

In the large number of the regulating portions 101, a separation S between two adjacent regulating portions 101, that is, a separation between vertexes of steep surfaces 101 a is set to a length that is less than a moving amount of the chevron-shaped plate 91 a of the sheet presence/absence detecting actuator 91 from the initial position to the pressed position. For example, in a case where the moving amount of the chevron-shaped plate 91 a of the sheet presence/absence detecting actuator 91 is set to 2 mm, the separation S is set to a length which is less than 2 mm, for example, 1.2 mm. Note that, separations S each for two adjacent regulating portions 101 are not desired to be set to the same length (equal pitch), and in short, only desired to be set to a length that is less than the moving amount of the chevron-shaped plate 91 a.

Furthermore, in the two adjacent regulating portions 101, a difference d between heights h of the vertexes of the steep surfaces 101 a is set to thickness of about two sheets of the recording sheets Ps that are placed on the manual tray 71.

In the regulating member 100, a length thereof in the sheet feeding direction E, that is, a length of an entirety of the large number of regulating portions 101 is set to about 15 mm in the present embodiment, for example.

Note that, in FIG. 6, a case where 15 regulating portions 101 are arranged is exemplified, but the number of regulating portions 101 to be arranged may be appropriately set.

As above, in the present embodiment, in a case where the small-sized recording sheet Ps is fed inside the image forming apparatus 1 by using the manual feeder 7, the manual tray 71 is positioned at the opened position and the extension tray 80 is positioned at the extension position, and in this state, the recording sheet Ps is placed on the placement surface 71 g of the manual tray 71.

In this state, in a case where the number of recording sheets Ps is large, the manual tray 71 is inclined toward the downstream side by the inclination angle θ1, and therefore the recording sheets Ps move to the downstream side in the sheet feeding direction E by their own weights. Thus, in the sheet presence/absence detecting actuator 91, the chevron-shaped plate 91 a receives the pressing to the downstream side in the sheet feeding direction E by the weights of the recording sheets Ps and rotates to the downstream side in the sheet feeding direction E against the urging force of the urging spring 91 c, and is thus deviated from the initial position. Accordingly, the sheet detecting unit 90 detects presence of the recording sheets Ps on the manual tray 71. In this state, rear end parts of the recording sheets Ps are positioned at the rear end part of the manual tray 71 within an arrangement range of the large number of regulating portions 101 of the regulating member 100.

On the other hand, in a case where the number of the recording sheets Ps on the manual tray 71 becomes, for example, one or two and the pressing of the recording sheets Ps to the downstream side in the sheet feeding direction E by their own weight becomes smaller than the urging force of the urging spring 91 c of the sheet presence/absence detecting actuator 91, the chevron-shaped plate 91 a of the sheet presence/absence detecting actuator 91 rotates to the upstream side in the sheet feeding direction E toward the position and is brought into a state of pushing back the recording sheets Ps to the upstream side in the sheet feeding direction E. However, in a case where the rear end parts of the recording sheets Ps contact the steep surface 101 a of any of the large number of regulating portions 101, movement further to the upstream side in the sheet feeding direction E is regulated or stopped by the regulating portion 101, and therefore the sheet presence/absence detecting actuator 91 does not move up to the initial position. Accordingly, the sheet detecting unit 90 reliably and accurately detects presence of the recording sheets Ps on the manual tray 71.

Here, the regulating member 100 is composed of the plurality of regulating portions 101, and furthermore, the regulating portions 101 are arranged so that the heights h, which are from the placement surface 71 g of the placement surface 71, are increased toward the upstream side in the sheet feeding direction E. Accordingly, even in a case where a plurality of kinds of recording sheets Ps that have different lengths in the sheet feeding direction E are selectively placed on the placement surface 71 g of the manual tray 71, a rear end part of a placed recording sheet Ps reliably contacts a vicinity of the vertex (a part corresponding to a difference d between the heights h of two adjacent regulating portions 101) of the steep surface 101 a of the closest regulating portion 101, which is positioned first on the upstream side in the sheet feeding direction E from the rear end part of the recording sheet Ps, among the plurality of regulating portions 101, to be locked, and therefore the regulating member 100 is not desired to be moved or adjusted to the upstream side or downstream side in the sheet feeding direction E each time the recording sheet Ps is placed, as of the related art.

Accordingly, for example, in a case where the recording sheet Ps to be placed on the manual tray 71 is a standard size sheet such as a postcard but has tolerance (for example, about 1.5 mm), and in a case where some positional displacement in the sheet feeding direction E occurs between a plurality of recording sheets Ps which are placed, and moreover, even in a case where sheets that have different lengths in the sheet feeding direction E and are variously customized are selectively placed, and even in a case where the number of such recording sheets Ps is about one or two, presence of the recoding sheet Ps on the manual tray 71 g is able to be accurately detected.

In addition, since the steep surface 101 a of any of the plurality of regulating portions 101 contacts a rear end surface of the recording sheet Ps to stop movement of the recording sheet Ps to the upstream side in the sheet feeding direction E, even in a case where the recording sheet Ps floats slightly from the placement surface 71 g of the manual tray 71, it is possible to reliably stop the movement of the recording sheet Ps to the upstream side in the sheet feeding direction E compared to a configuration of the related art in which a friction member is arranged on a placement surface to suppress the movement by a frictional force with a lower surface of a sheet.

Note that, in a case where there is no recording sheet Ps on the manual tray 71, since the chevron-shaped plate 91 a of the sheet presence/absence detecting actuator 91 is positioned at the initial position by the urging force of the urging spring 91 c, the sheet detecting unit 90 accurately detects absence of a recording sheet Ps on the manual tray 71.

In the present embodiment, the regulating member 100 is arranged at the rear end part of the manual tray 71, that is, a periphery of a connection portion of the manual tray 71 and the extension tray 80, and the inclination angle θ2 of the extension tray 80 is set to be larger than the inclination angle θ1 of the manual tray 71 (θ2>θ1). Accordingly, in a case where the large-sized recording sheet Pl is placed over the placement surface lip of the manual tray 71 and the placement surface 80 e of the extension tray 80, as understood from FIG. 4, an empty space P that is surrounded by the periphery of the connection portion of the manual tray 71 and extension tray 80 and the recording sheet Pl is generated below the recording sheet Pl, and the regulating member 100 is positioned in the empty space P. Accordingly, on feeding of the large-sized recording sheet Pl, the regulating member 100 does not interfere with a moving operation of the recording sheet Pl in the sheet feeding direction E. Thus, it is possible to easily feed the large-sized recording sheet Pl without performing a manual operation such as removal of the regulating member 100.

Note that, since the large-sized recording sheet Pi is heavier than the small-sized recording sheet Ps, in the case where the large-sized recording sheet Pl is placed, even when the number of recording sheets Pl is one or two, the chevron-shaped plate 91 a of the sheet presence/absence detecting actuator 91 rotates toward the downstream side in the sheet feeding direction E against the urging force of the urging spring 91 c by the weight and is thus deviated from the initial position. Therefore, the sheet detecting unit 90 accurately detects placement of a large-sized recording sheet Pl even in the case where the number of large-sized recording sheets Pl is one or two.

Moreover, in the present embodiment, in the plurality of regulating portions 101 of the regulating member 100, the separation between adjacent regulating portions 101 is set to a length (for example, 1.2 mm) less than an operation amount or the sheet presence/absence detecting actuator 91, that is, a moving amount (for example, 2 mm) of the chevron-shaped plate 91 a from the pressed position to the initial position. Accordingly, even in the case where the chevron-shaped plate 91 a of the sheet presence/absence detecting actuator 91 pushes back the recording sheet Ps by the urging spring 91 c toward the upstream side in the sheet feeding direction E, the rear end part of the recording sheet Ps is locked by the steep surface 101 a of any one of the plurality of regulating portions 101 at a middle stage of a way where the chevron-shaped plate 91 a reaches the initial position, and thus movement further toward the upstream side in the sheet feeding direction E is stopped. Therefore, the chevron-shaped plate 91 a of the sheet presence/absence detecting actuator 91 does not reach the initial position, and therefore the sheet detecting unit 90 accurately detects presence of the recording sheet Ps on the manual tray 71.

Moreover, in the present embodiment, the two regulating members 100 are arranged on both right and left sides across the center line I within the lateral width of the small-sized recording sheet Ps that is placed on the manual tray 71. Accordingly, even in a case where the sheet presence/absence detecting actuator 91 pushes back a leading end part of the recording sheet Ps at a position deviated from the center line 1, the recording sheet Ps is positioned to be symmetric with respect to the center line 1 by the two regulating members 100, and therefore occurrence of positional displacement to the left or right is suppressed.

Embodiment 2

FIG. 7 illustrates a principal part of a sheet feeder of Embodiment 2.

The regulating member 100 is formed in the saw-tooth shape in Embodiment 1 described above but is formed in a comb shape in the present embodiment.

That is, in the regulating member 100 illustrated in FIG. 7, a plurality of comb teeth extending in a line toward the upstream side in the sheet feeding direction E are provided at the rear end part of the manual tray 71 and are set as the plurality of regulating portions 101. The plurality of regulating portions 101 are each formed in a rectangular shape that extends upward from the placement surface 71 g, and are arranged so that heights of the regulating portion 101 from the placement surface 71 g are increased toward the upstream side in the sheet feeding direction E, similarly to Embodiment 1.

Embodiment 3

FIG. 8 illustrates a principal part of a sheet feeder of Embodiment 3.

In the present embodiment, the regulating member 100 is formed in a brush shape. That is, in FIG. 8, a large number of linear bristle materials extending upward from the placement surface 71 g are arranged in the sheet feeding direction E and the lateral width direction and are set as a large number of regulating portions 101, and the large number of regulating portions 101 are arranged so that heights thereof, which are from the placement surface 71 g, are increased toward the upstream side in the sheet feeding direction E.

In the present embodiment, the large number of regulating portions 101 are arranged toward the upstream side in the sheet feeding direction E, and therefore it is possible to suppress an amount of pushing back the recording sheet Ps, which is placed on the manual tray 71, to the upstream side in the sheet feeding direction E to a minimum.

Note that, in the aforementioned description, the regulating member 100 is formed in the saw-tooth shape, the comb shape, or the brush shape, but may alternatively be formed in a stepwise shape or a shape constituted by a plurality of continuous ribs. Furthermore, a sponge, a sheet with high friction, or Velcro (registered trademark) may be used and a shape of such a material may be configured in which a height is increased toward the upstream side in the sheet feeding direction E.

In Embodiments described above, the disclosure is applied to the manual feeder 7 but, in addition thereto, needleless to say, may be applied to the document reading device 2 or the automatic document feeder 3 to accurately detect presence/absence of a document that is placed thereon.

The disclosure may be implemented in other various forms without departing from the spirit or features thereof. Accordingly, any of Embodiments described above is merely illustrative and should not be considered as limiting. All modifications and changes falling in a range equivalent to the scope of the claims of the disclosure are included in the scope of the disclosure.

The disclosure is useful when being applied, as a sheet feeder, to a sheet feeder or an image forming apparatus including the same because it is possible to reliably and accurately detect presence of a sheet on a sheet placing table without performing any manual operation such as change or adjustment of a position of a regulating member arranged on the sheet placing table, or removal of the regulating member, even in a case where the number of sheets on the sheet placing table becomes, for example, about one or two.

The present disclosure contains subject matter related to that disclosed in Japanese Priority Patent Application JP 2018-126997 filed. in the Japan Patent Office on Jul. 3, 2018, the entire contents of which are hereby incorporated by reference.

It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof. 

What is claimed is:
 1. A sheet feeder that feeds a sheet to an image forming apparatus, the sheet feeder comprising: a sheet placing table that has a placement surface on which a sheet is placed and that is inclined downward toward a downstream side in a sheet feeding direction in which the sheet is fed to the image forming apparatus; a sheet detecting unit that has an operation piece which presses an end of the sheet on the downstream side in the sheet feeding direction toward an upstream side in the sheet feeding direction with predetermined pressure and that detects presence or absence of the sheet by an operation of the operation piece; and at least one regulating member that is arranged in a vicinity of an end part of the sheet placing table on the upstream side in the sheet feeding direction and that regulates movement of the sheet to the upstream side in the sheet feeding direction, wherein the at least one regulating member has a plurality of regulating portions having different heights from the placement surface of the sheet placing table, and the plurality of regulating portions are arranged so that the heights are increased toward the upstream side in the sheet feeding direction.
 2. The sheet feeder according to claim 1, wherein the sheet placing table is a manual tray, and a plurality of kinds of sheets that have different lengths in the sheet feeding direction are selectively placed on the manual tray.
 3. The sheet feeder according to claim 1, wherein an extended sheet placing table for a large-sized sheet, which is inclined downward toward the downstream side in the sheet feeding direction, is connected to the end part of the sheet placing table on the upstream side in the sheet feeding direction, as angle by which the extended sheet placing table is inclined is set to be larger than an angle by which the sheet placing table is inclined, and the at least one regulating member is arranged at a position in a vicinity of a connection portion of the sheet placing table and the extended sheet placing table.
 4. The sheet feeder according to claim 1, wherein the at least one regulating member includes two regulating members, and the two regulating members are arranged within a width of the sheet in a direction orthogonal to the sheet feeding direction on each of right and left sides across a center of the width.
 5. The sheet feeder according to claim 1, wherein in the plurality of regulating portions, a separation between adjacent regulating portions is set to a length less than a moving amount of the operation piece to the upstream side in the sheet feeding direction.
 6. The sheet feeder according to claim 1, wherein the plurality of regulating portions are formed in a stepwise shape, a comb shape, or a brush shape.
 7. An image forming apparatus comprising: the sheet feeder according to claim 1; a taking-in unit that takes the sheet, which is placed on the sheet placing table, inside the image forming apparatus; and an image forming unit that forms an image on the sheet which is taken in by the taking-in unit. 